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Abstract:

The organic-inorganic composite particles can be dispersed as primary
particles in a solvent and/or a resin and have a plurality of mutually
different organic groups on the surface of inorganic particles.

Claims:

1. Organic-inorganic composite particles that can be dispersed as primary
particles in a solvent and/or a resin, and that have a plurality of
mutually different organic groups on a surface of inorganic particles.

2. The organic-inorganic composite particles according to claim 1,
produced in a high-temperature solvent.

3. The organic-inorganic composite particles according to claim 1,
produced in a high-temperature, high-pressure solvent.

4. The organic-inorganic composite particles according to claim 1,
wherein the plurality of organic groups are organic groups each having a
different number of main-chain atoms and/or organic groups each having a
different main-chain molecular structure.

5. The organic-inorganic composite particles according to claim 4,
wherein the plurality of organic groups are hydrocarbon groups each
having a different number of main-chain carbon atoms and/or hydrocarbon
groups each having a different main-chain molecular structure.

6. The organic-inorganic composite particles according to claim 1,
wherein at least one of the plurality of organic groups is a functional
group-containing organic group at least comprising a functional group in
a side chain or at a terminal, and when two or more of the organic groups
are the functional group-containing organic groups, the organic groups
each have a different functional group or a different number of
main-chain atoms.

7. The organic-inorganic composite particles according to claim 6,
wherein at least one of the plurality of organic groups is a functional
group-containing hydrocarbon-based group comprising at least a
hydrocarbon group and a functional group bonded to the hydrocarbon group,
and when two or more of the organic groups are the functional
group-containing hydrocarbon-based groups, the hydrocarbon-based groups
each have a different functional group or a different number of
main-chain carbon atoms.

8. A particle dispersion comprising: a solvent, and organic-inorganic
composite particles that are dispersed as primary particles in the
solvent and that have a plurality of mutually different organic groups on
a surface of inorganic particles.

9. A particle-dispersed resin composition comprising: a resin, and
organic-inorganic composite particles that are dispersed as primary
particles in the resin and that have a plurality of mutually different
organic groups on a surface of inorganic particles.

10. A method for producing organic-inorganic composite particles,
comprising treating inorganic particles and a plurality of mutually
different organic compounds at a high temperature to treat a surface of
the inorganic particles with the plurality of organic compounds, the
plurality of organic compounds comprising organic groups and a linker
that can be bonded to the surface of the inorganic particles, the organic
groups being mutually different.

Description:

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority of Japanese Patent
Application No. 2010-091577, filed on Apr. 12, 2010, and Japanese Patent
Application No. 2010-172306, filed on Jul. 30, 2010, the entire contents
of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to organic-inorganic composite
particles, a particle dispersion, a particle-dispersed resin composition,
and a method for producing organic-inorganic composite particles.
Specifically, the present invention relates to a particle dispersion and
a particle-dispersed resin composition for use in various industrial
applications including optical applications, to organic-inorganic
composite particles dispersed in such a dispersion and a composition, and
to a production method therefor.

[0004] 2. Description of Related Art

[0005] Nano-scale particles (nanoparticles) have been used in various
industrial applications including optical applications.

[0006] For example, Japanese Unexamined Patent Publication No. 2005-194148
proposes dispersing, in a solvent or a resin, organic-modified fine
particles obtained by a hydrothermal synthesis using metal oxide
particles and an organic modifier.

SUMMARY OF THE INVENTION

[0007] However, organic-modified fine particles are problematic in that
the organic-modified fine particles agglomerate when they are blended in
a solvent or a resin in a high proportion.

[0008] An object of the present invention is to provide organic-inorganic
composite particles that can be dispersed uniformly or nearly uniformly
as primary particles in a solvent and/or a resin even when blended in a
high proportion and a production method therefor as well as a particle
dispersion and a particle-dispersed resin composition containing the
organic-inorganic composite particles.

[0009] The organic-inorganic composite particles of the present invention
can be dispersed as primary particles in a solvent and/or a resin and
have a plurality of mutually different organic groups on the surface of
inorganic particles.

[0010] It is preferable that the organic-inorganic composite particles of
the present invention are produced in a high-temperature solvent.

[0011] It is preferable that the organic-inorganic composite particles of
the present invention are produced in high-temperature, high-pressure
water.

[0012] In the organic-inorganic composite particles of the present
invention, it is preferable that the plurality of organic groups are
organic groups each having a different number of main-chain atoms and/or
organic groups each having a different main-chain molecular structure,
and it is preferable that the plurality of organic groups are hydrocarbon
groups each having a different number of main-chain carbon atoms and/or
hydrocarbon groups each having a different main-chain molecular
structure.

[0013] In the organic-inorganic composite particles of the present
invention, it is preferable that at least one of the plurality of organic
groups is a functional group-containing organic group at least containing
a functional group in a side chain or at a terminal, and when two or more
of the organic groups are the functional group-containing organic groups,
the organic groups each have a different functional group or a different
number of main-chain atoms, and it is preferable that at least one of the
plurality of organic groups is a functional group-containing
hydrocarbon-based organic group containing at least a hydrocarbon group
and a functional group bonded to the hydrocarbon group, and when two or
more of the organic groups are the functional group-containing
hydrocarbon-based organic groups, the hydrocarbon-based groups each have
a different functional group or a different number of main-chain carbon
atoms.

[0014] The particle dispersion of the present invention contains a solvent
and the aforementioned organic-inorganic composite particles that are
dispersed as primary particles in the solvent The particle-dispersed
resin composition of the present invention contains a resin and the
aforementioned organic-inorganic composite particles that are dispersed
as primary particles in the resin.

[0015] The method for producing organic-inorganic composite particles of
the present invention includes treating inorganic particles and a
plurality of mutually different organic compounds at a high temperature
to treat the surface of the inorganic particles with the plurality of
organic compounds, the plurality of organic compounds contain organic
groups and a linker that can be bonded to the surface of the inorganic
particles, and the organic groups are mutually different.

[0016] The organic-inorganic composite particles of the present invention
obtained according to the production method of the present invention can
be dispersed as primary particles in a solvent and/or a resin in a high
proportion, exhibiting excellent dispersibility in a solvent and/or a
resin.

[0017] Accordingly, in the particle dispersion and the particle-dispersed
resin composition of the present invention, organic-inorganic composite
particles are dispersed highly uniformly. Moreover, it is possible that
the organic-inorganic composite particles are dispersed highly uniformly
in a high proportion.

[0018] As a result, a solution chemistry reaction can be uniformly and
more efficiently carried out on the organic groups bonded to the
inorganic particles in the particle-dispersed composition. In other
words, modification of the organic groups of organic-inorganic composite
particles can be performed uniformly.

[0019] The particle-dispersed resin composition obtained from the particle
dispersion composition has excellent transparency, and a
particle-dispersed resin article formed from the particle-dispersed resin
composition maintains excellent transparency.

[0020] Therefore, the particle-dispersed resin article of the present
invention can be used in various applications where transparency is
required.

DETAILED DESCRIPTION OF THE INVENTION

[0021] The organic-inorganic composite particles of the present invention
can be dispersed as primary particles in a solvent and/or a resin and
have a plurality of mutually different organic groups on the surface of
inorganic particles.

[0022] Specifically, the organic-inorganic composite particles can be
obtained by treating the surface of inorganic particles using organic
compounds.

[0023] One kind of organic-inorganic composite particle may be used or two
or more kinds may be used in combination.

[0024] Examples of inorganic compounds (starting inorganic substances)
that form inorganic particles include oxide, composite oxide, carbonate,
and the like.

[0025] Examples of inorganic substances that form inorganic particles
include metals including metallic elements such as main group elements
and transition elements; nonmetals including nonmetallic elements such as
boron and silicon; inorganic compounds containing metallic elements
and/or nonmetals; and the like.

[0026] Examples of metallic elements and nonmetallic elements (IUPAC,
1989) include, assuming that a border is created by boron (B) of the IIIB
group, silicon (Si) of the IVB group, arsenic (As) of the VB group,
tellurium (Te) of the VIB group, and astatine (At) of the VIM group in
the long-form periodic table (IUPAC, 1989), these elements and elements
that are located on the left side as well as the lower side of the border
in the long-form periodic table. Specific examples include the group IIIA
elements such as Sc and Y; the group IVA elements such as Ti, Zr, and Hf;
the group VA elements such as V, Nb, and Ta; the group VIA elements such
as Cr, Mo, and W; the group VITA elements such as Mn and Re; the group
VIII elements such as Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, and Pt; the group
IB elements such as Cu, Ag, and Au; the group IIB elements such as Zn,
Cd, and Hg; the group MB elements such as B, Al, Ga, In, and Tl; the
group IVB elements such as Si, Ge, Sn, and Pb; the group VB elements such
as As, Sb, and Bi; the group VIB elements such as Te and Po; the
lanthanide series elements such as La, Ce, Pr, and Nd; the actinium
series elements such as Ac, Th, and U; and the like.

[0031] The composite oxides are compounds of oxygen and a plurality of
elements, and the plurality of elements may be a combination of at least
two elements selected from the elements other than oxygen present in the
aforementioned oxides, the group I elements, and the group II elements.

[0032] Examples of the group I elements include alkali metals such as Li,
Na, K, Rb, and Cs. Examples of the group II elements include alkaline
earth metals such as Be, Mg, Ca, Sr, Ba, and Ra.

[0033] Preferable examples of combinations of elements include a
combination of a group II element and a group IVB element, a combination
of a group II element and a group VIII element, a combination of a group
II element and a group WA element, and other combinations that contain at
least a group II element.

[0037] Composite oxides may be used singly or as a combination of two or
more.

[0038] As for carbonates, examples of elements that combine with carbonic
acid include alkali metals, alkaline earth metals, and the like. Examples
of alkali metals and alkaline earth metals are as described above.

[0039] Among the elements that combine with carbonic acid, alkaline earth
metals are preferable.

[0040] Specifically, preferable carbonates include those containing
alkaline earth metals, and examples of such carbonates include beryllium
carbonate, magnesium carbonate, calcium carbonate, strontium carbonate,
barium carbonate, radium carbonate, and the like. Carbonates may be used
singly or as a combination of two or more.

[0041] Sulfates are compounds of sulfate ions (SO42-) and metal
cations (more specifically, compounds formed by the substitution of
hydrogen atoms of sulfuric acid (H2SO4) with a metal), and
examples of metals contained in sulfates include alkali metals, alkaline
earth metals, and the like. Examples of alkali metals and alkaline earth
metals are as described above.

[0044] Sulfates may be used singly or as a combination of two or more.

[0045] The plurality of organic compounds (starting organic materials)
are, for example, mutually different organic group-introducing compounds
for introducing (distributing) mutually different organic groups onto the
surface of inorganic particles. Specifically, the organic compounds
contain mutually different organic groups and a linker that can be bonded
to the surface of inorganic particles.

[0046] The linker may be suitably selected according to the type of
inorganic particle, and examples include functional groups (first
functional group, binding functional group) such as a carboxyl group, a
phosphate group (--PO(OH)2, phosphono group), an amino group, a
sulfo group, a hydroxyl group, a thiol group, an epoxy group, an
isocyanate group (cyano group), a nitro group, an azo group, a silyloxy
group, an imino group, an aldehyde group (acyl group), a nitrile group, a
vinyl group (polymerizable group), and the like. Preferable examples
include a carboxyl group, a phosphate group, an amino group, a sulfo
group, a hydroxyl group, a thiol group, an epoxy group, an azo group, a
vinyl group, and the like, with a carboxyl group and a phosphate group
being particularly preferable.

[0047] The carboxyl group includes its esters. To be specific, the
carboxyl group includes alkoxy carbonyl (carboxylic acid alkyl ester)
such as ethoxy carbonyl (carboxylic acid ethylester) and the like.

[0048] The phosphate group includes its esters. For example, the phosphate
group includes dialkoxy phosphonyl groups (phosphoric acid dialkyl ester)
such as diethoxy phosphonyl (phosphoric acid diethylester) and the like.

[0049] The linker is selected appropriately in accordance with the
above-described inorganic particles. To be specific, when the inorganic
particles are composed of cerium oxide or strontium carbonate, for
example, a carboxyl group is selected, and when the inorganic particles
are composed of titanium oxide, for example, a phosphate group is
selected.

[0050] One or more of these linkers are contained in each organic
compound. In particular, a linker is bonded to a terminal or a side chain
of an organic group.

[0051] Examples of the plurality of mutually different organic groups
include organic groups each having a different number of main-chain atoms
and/or organic groups each having a different main-chain molecular
structure. Specific examples of the plurality of organic groups include
hydrocarbon groups each having a different number of main-chain carbon
atoms and/or hydrocarbon groups each having a different main-chain
molecular structure.

[0052] Examples of such hydrocarbon groups include aliphatic groups,
alicyclic groups, araliphatic groups (these are also called as aralkyl
groups), aromatic groups, and the like.

[0065] Regarding the plurality of organic groups, at least one of the
organic groups is a functional group-containing organic group at least
containing a functional group (second functional group) in a side chain
or at a terminal, and when two or more of the organic groups are
functional group-containing organic groups, the organic groups each have
a different functional group or a different number of main-chain atoms.

[0066] Preferably, regarding the plurality of organic groups, at least one
of the organic groups is a functional group-containing hydrocarbon-based
organic group at least containing a hydrocarbon group and a functional
group bonded to the hydrocarbon group, and when two or more of the
organic groups are functional group-containing hydrocarbon-based organic
groups, the organic groups each have a different functional group or a
different number of main-chain carbon atoms.

[0067] The hydrocarbon group contained in a functional group-containing
hydrocarbon-based organic group may be the same as those described above.

[0068] The functional group-containing hydrocarbon-based organic group has
a foregoing hydrocarbon group and a functional group bonded thereto
(active functional group, second functional group).

[0069] That is, the functional group is regarded as an active group for
activating the surface of inorganic particles and, in the organic
compounds, is bonded to a terminal (the terminal (second terminal)
opposite the terminal to which the linker is bonded (first terminal)) or
a side chain of the hydrocarbon group. Therefore, the functional group
can also be used as an active group for activating the surface of
inorganic composite particles.

[0070] Examples of the functional group (second functional group) include
a carboxyl group, a hydroxyl group, a phosphate group (--PO(OH)2,
phosphono group), a thiol group, an amino group, a sulfo group, a
carbonyl group, an epoxy group, an isocyanate group, a nitro group, an
azo group, a silyloxy group, an imino group, an acyl group, an aldehyde
group, a cyano group, a nitrile group, a vinyl group (polymerizable
group), a halogen group (e.g., bromo), and the like. Preferable examples
of the functional group include a carboxyl group, a phosphate group, an
amino group, a sulfo group, a hydroxyl group, a thiol group, an epoxy
group, an azo group, an amino group, a carbonyl group, a vinyl group, and
the like.

[0071] One or more of these functional groups may be contained in each
organic compound.

[0074] Examples of carboxyl group-containing organic groups also include
alkoxycarbonyl aliphatic groups including alkoxycarbonyl saturated
aliphatic groups such as 3-(ethoxy-carbonyl)propyl,
6-(ethoxy-carbonyl)hexyl, 10-(ethoxy-carbonyl)decyl, and the like.

[0078] Examples of thiol group-containing organic groups include
mercaptosaturated aliphatic groups (mercaptoaliphatic groups) such as
10-mercaptodecyl; and the like.

[0079] Examples of amino group-containing organic groups include
aminosaturated aliphatic groups (aminoaliphatic groups) such as
6-aminohexyl; aminoaraliphatic groups such as 6-aminophenylhexyl; and the
like.

[0080] Examples of sulfo group-containing organic groups include
sulphosaturated aliphatic groups (sulphoaliphatic groups) such as
6-sulphohexyl; sulphoaraliphatic groups such as 6-sulphophenylhexyl; and
the like.

[0081] Examples of carbonyl group-containing organic groups include
oxosaturated aliphatic groups (oxoaliphatic groups) such as 4-oxopentyl,
5-oxohexyl, and 7-oxooctyl; and the like.

[0084] Examples of carboxyl group-containing organic compounds also
include, when the linker (first functional group) is a phosphate group
and the functional group (second functional group) is a carboxyl group
(to be more specific, when a phosphate group is bonded to inorganic
particles composed of titanium oxide), and/or when the linker (first
functional group) is a carboxyl group and the functional group (second
functional group) is a phosphate group (to be more specific, when a
carboxyl group is bonded to inorganic particles composed of cerium oxide
or strontium carbonate), a compound having both of a phosphate group and
a carboxyl group including monophosphonocarboxylic acid such as
3-phosphonopropionic acid, 6-phosphono hexanoic acid, 8-phosphono
octanoic acid, 10-phosphono decanoic acid, and 6-phosphonophenyl hexanoic
acid; and dialkoxy phosphonyl carboxylic acid alkyl ester such as
3-(diethoxy-phosphonyl) propionic acid ethylester,
6-(diethoxy-phosphonyl) hexanoic acid ethylester, 8-(diethoxy-phosphonyl)
octanoic acid ethylester, and 10-(diethoxy-phosphonyl) decanoic acid
ethylester. The above-described compound having both of a phosphate group
and a carboxyl group is also a phosphate group-containing organic
compound.

[0086] Examples of thiol gorup-containing organic compounds include, when
the linker (first functional group) is a carboxyl group and the
functional group (second functional group) is a thiol group,
10-carboxydecanethiol and the like.

[0087] Examples of amino group-containing organic compounds include, when
the linker (first functional group) is a carboxyl group and the
functional group (second functional group) is an amino group,
monoaminocarboxylic acid, and specific examples include 6-aminohexanoic
acid, 6-aminophenylhexanoic acid, and the like.

[0088] Examples of sulfo group-containing organic compounds include, when
the linker (first functional group) is a carboxyl group and the
functional group (second functional group) is a sulfo group,
monosulfocarboxylic acid, and specific examples include 6-sulfohexanoic
acid, 6-sulfophenylhexanoic acid, and the like.

[0089] Examples of carbonyl group-containing organic compounds include,
when the linker (first functional group) is a carboxyl group and the
functional group (second functional group) is a carbonyl group,
monocarbonylcarboxylic acid, and specific examples include 4-oxopentanoic
acid (4-oxovaleric acid), 5-oxohexanoic acid (5-oxocaproic acid), and the
like.

[0090] In the plurality of organic compounds, the organic groups are
mutually different.

[0091] The plurality of organic groups are, for example, hydrocarbon
groups each having a different number of main-chain carbon atoms. An
example of such a combination may be a combination of at least two
hydrocarbon groups selected from the group consisting of aliphatic
groups, alicyclic groups, araliphatic groups, and aromatic groups each
having a different number of carbon atoms (first combination). Preferable
may be a combination of hexyl and decyl, a combination of hexyl and
ethylhexyl, a combination of phenyl and 6-phenylhexyl, a combination of
propylcyclohexyl and cyclohexyl, a combination of decyl and
trimethylhexyl, or a like combination.

[0092] Among the plurality of organic groups, at least one organic group
may be a foregoing functional group-containing hydrocarbon-based organic
group.

[0093] In this case, the plurality of organic groups are, for example, a
combination of at least one hydrocarbon group and at least one functional
group-containing hydrocarbon-based organic group (second combination) or
a combination of at least two functional group-containing
hydrocarbon-based organic groups (third combination).

[0094] As for the second combination, the combination of at least two
groups may be, for example, a combination of an aliphatic group and a
hydroxyaliphatic group, a combination of an aliphatic group and a carboxy
aliphatic group, a combination of an aliphatic group and an oxoaliphatic
group, a combination of an aliphatic group and a mercapto aliphatic
group, and the like. In the second combination, the number of carbon
atoms is not particularly limited, and examples thereof include a
combination of a hydrocarbon group and a functional group-containing
hydrocarbon organic group having mutually different numbers of carbon
atoms (to be specific, a combination of an aliphatic group having 1 to 9
carbon atoms and a functional group-containing hydrocarbon organic group
having 10 to 20 carbon atoms).

[0095] Examples of the combination of an aliphatic group and a
hydroxyaliphatic group may be a combination of decyl and 6-hydroxyhexyl,
and a combination of hexyl and 6-hydroxyhexyl.

[0096] Examples of the combination of an aliphatic group and a carboxy
aliphatic group include a combination of methyl and 3-carboxypropyl, a
combination of methyl and 6-carboxyhexyl, a combination of methyl and
10-carboxydecyl, a combination of hexyl and 10-carboxydecyl, and the
like. Examples of the combination of an aliphatic group and a carboxy
aliphatic group also include a combination of an aliphatic group and an
alkoxycarbonyl aliphatic group such as a combination of methyl and
10-(ethoxy-carbonyl)decyl, a combination of octyl and
10-(ethoxy-carbonyl)decyl, a combination of decyl and
10-(ethoxy-carbonyl)decyl, a combination of methyl, decyl, and
10-(ethoxy-carbonyl)decyl, a combination of octyl, decyl, and
10-(ethoxy-carbonyl)decyl, and the like.

[0097] Examples of the combination of an aliphatic group and an
oxoaliphatic group include a combination of propyl and 4-oxopentyl, a
combination of hexyl and 7-oxooctyl, and the like.

[0098] Examples of the combination of an aliphatic group and a mercapto
aliphatic group include a combination of hexyl and 10-carboxydecanethiol
and the like.

[0099] As for the third combination, in the at least two (i.e., two or
more) functional group-containing organic groups, the functional groups
are different to each other. As for the third combination, an example of
the combination of the at least two functional group-containing organic
groups may be a combination of two functional group-containing
hydrocarbon-based organic groups selected from the group consisting of
carboxyl group-containing organic groups, hydroxyl group-containing
organic groups, phosphate group-containing organic groups, thiol
group-containing organic groups, amino group-containing organic groups,
sulfo group-containing organic groups, and carbonyl group-containing
organic groups. A combination of a hydroxyaliphatic group and an
oxoaliphatic group, a combination of a carboxy aliphatic group and an
alkoxycarbonyl aliphatic group, a combination of carboxy aliphatic groups
having mutually different numbers of carbon atoms, and a combination of
alkoxycarbonyl aliphatic groups having mutually different numbers of
carbon atoms are preferable.

[0100] An example of the combination of a hydroxyaliphatic group and an
oxoaliphatic group may be a combination of 6-hydroxyhexyl and 5-oxohexyl.

[0101] An example of the combination of a carboxy aliphatic group and an
alkoxycarbonyl aliphatic group may be a combination of 3-carboxypropyl
and 10-(ethoxy-carbonyl)decyl.

[0102] Examples of the combination of carboxy aliphatic groups having
mutually different numbers of carbon atoms include a combination of a
carboxy aliphatic group having carbon atoms of less than 6 and a carboxy
aliphatic group having carbon atoms of 6 or more, to be specific, a
combination of 3-carboxypropyl and 6-carboxyhexyl.

[0103] Examples of the combination of alkoxycarbonyl aliphatic groups
having mutually different numbers of carbon atoms include a combination
of an alkoxycarbonyl aliphatic group having carbon atoms of less than 6
and an alkoxycarbonyl aliphatic group having carbon atoms of 6 or more,
to be specific, a combination of 3-(ethoxy-carbonyl)propyl and
6-(ethoxy-carbonyl)hexyl.

[0104] The plurality of mutually different organic groups are present on
the surface of common inorganic particles in the organic-inorganic
composite particles. That is, the mutually different organic groups coat
the surface of the same inorganic particles. Specifically, the mutually
different organic groups stretch outward from the surface of the common
inorganic particles via a linker.

[0105] The organic-inorganic composite particles can be obtained by
subjecting an inorganic substance and a plurality of mutually different
organic compounds to a reaction treatment, preferably a high-temperature
treatment.

[0106] The organic-inorganic composite particles are produced by
subjecting an inorganic substance and a plurality of mutually different
organic compounds to a reaction treatment, preferably a high-temperature
treatment.

[0107] The high-temperature treatment is carried out in a solvent.
Examples of solvents include water and the aforementioned organic
compounds.

[0108] Specifically, an inorganic substance and a plurality of mutually
different organic compounds are subjected to a high-temperature treatment
in water under high pressures (hydrothermal synthesis: hydrothermal
reaction) or an inorganic substance is subjected to a high-temperature
treatment in a plurality of mutually different organic compounds (a
high-temperature treatment in a plurality of mutually different organic
compounds) to give organic-inorganic composite particles. That is, the
surface of inorganic particles formed of an inorganic substance is
treated with a plurality of mutually different organic compounds to give
organic-inorganic composite particles.

[0109] For example, in a hydrothermal synthesis, an inorganic substance
and a plurality of mutually different organic compounds are reacted under
high-temperature, high-pressure conditions in the presence of water
(first hydrothermal synthesis).

[0110] The inorganic substance subjected to the first hydrothermal
synthesis is preferably a carbonate or a sulfate.

[0111] The mutually different organic compounds correspond to the mutually
different organic groups described above. Specifically, the plurality of
mutually different organic compounds contain a plurality of mutually
different organic groups corresponding to the above-described first,
second, or third combination.

[0112] As for the proportions of respective ingredients, the total
proportion of the plurality of organic compounds is, for example, 1 to
1500 parts by mass, preferably 5 to 500 parts by mass, and more
preferably 5 to 250 parts by mass, and the proportion of water is, for
example, 50 to 8000 parts by mass, preferably 80 to 6600 parts by mass,
and more preferably 100 to 4500 parts by mass, per 100 parts by mass of
inorganic substance.

[0113] Since the density of the plurality of organic compounds is normally
0.8 to 1.1 g/mL, the total proportion of the plurality of organic
compounds is, for example, 0.9 to 1880 mL, preferably 4.5 to 630 mL, and
more preferably 4.5 to 320 mL, per 100 g of inorganic substance.

[0114] The total molar proportion of the plurality of organic compounds
is, for example, 0.01 to 1000 mol, preferably 0.02 to 50 mol, and more
preferably 0.1 to 10 mol, per one mol of inorganic substance.

[0115] As for the total proportion of the plurality of organic compounds,
when a plurality of (e.g., two) different organic groups are contained,
specifically, the proportion of one organic compound relative to the
other organic compound in terms of mass, volume, and mole is, in all
cases, for example, 1:99 to 99:1 and preferably 10:90 to 90:10.

[0116] More specifically, when the plurality of mutually different organic
groups are of the first combination, for example, when the plurality of
mutually different organic compounds each have a different number of
carbon atoms, the proportion of one organic compound having fewer carbon
atoms to the other organic compound having more carbon atoms in terms of
mass, volume, and mole is, in all cases, for example, 10:90 to 99.9:0.1
and preferably 20:80 to 99:1.

[0117] When the plurality of mutually different organic groups are of the
second combination, for example, when the plurality of mutually different
organic compounds are a combination of the first organic compound and the
second organic compound, the proportion of the first organic compound to
the second organic compound in terms of mass, volume, and mole is, in all
cases, for example, 1:99 to 99:1 and preferably 10:90 to 90:10.

[0118] When the plurality of organic groups are of the third combination,
for example, when the plurality of organic compounds are a combination of
a hydroxyaliphatic acid and an oxoaliphatic acid each having a different
number of carbon atoms, the proportion of the hydroxyaliphatic acid to
the oxoaliphatic acid in terms of mass, volume, and mole is, in all
cases, for example, 1:99 to 99:1 and preferably 10:90 to 90:10.

[0119] Since the density of water is normally about 1 g/mL, the proportion
of water is, for example, 50 to 8000 mL, preferably 80 to 6600 mL, and
more preferably 100 to 4500 mL, per 100 g of inorganic compound.

[0120] Specifically, as for the reaction conditions in a hydrothermal
reaction, the heating temperature is, for example, 100 to 500° C.
and preferably 200 to 400° C. The pressure is, for example, 0.2 to
50 MPa, preferably 1 to 50 MPa, and more preferably 10 to 50 MPa. The
reaction time is, for example, 1 to 200 minutes and preferably 3 to 150
minutes. Meanwhile, when a continuous reactor is used, the reaction time
may be 1 minute or less.

[0121] The reaction products obtained after the reaction mainly include a
precipitate mostly precipitating in water and a deposit adhering to the
inner wall of an airtight container.

[0122] The precipitate is obtained by, for example, sedimentation
separation in which the reaction products are subjected to gravity or a
centrifugal field to settle the precipitate. Preferably, the precipitate
is obtained as the precipitate of the reaction products by centrifugal
sedimentation (centrifugal separation) in which settling takes place in a
centrifugal field.

[0123] The deposit is collected with, for example, a spatula or the like.

[0124] It is also possible that a solvent is added to the reaction
products to wash away the unreacted organic compounds (that is, organic
compounds are dissolved in a solvent) and then the solvent is removed and
the reaction products are recovered (isolated).

[0125] Examples of solvents include alcohols (hydroxyl group-containing
aliphatic hydrocarbons) such as methanol, ethanol, propanol, and
isopropanol; ketones (carbonyl group-containing aliphatic hydrocarbons)
such as acetone, methyl ethyl ketone, cyclohexanone, and cyclopentanone;
aliphatic hydrocarbons such as pentane, hexane, and heptane; halogenated
aliphatic hydrocarbons such as dichloromethane, chloroform, and
trichloroethane; halogenated aromatic hydrocarbons such as chlorobenzene
and dichlorobenzene; ethers such as tetrahydrofuran; aromatic
hydrocarbons such as benzene, toluene, and xylene; aqueous pH controlling
solutions such as aqueous ammonia; and the like. Alcohols are preferable.

[0126] The reaction products after washing are isolated from the solvent
(supernatant) by, for example, filtration, decantation, or a similar
technique, and then recovered. Thereafter, the reaction products may be
dried if necessary by, for example, heating or in an air stream.

[0127] In this manner, organic-inorganic composite particles having a
plurality of mutually different organic groups on the surface of
inorganic particles are obtained.

[0128] In the first hydrothermal synthesis, the pre-reaction inorganic
substance and the post-reaction inorganic substance that forms inorganic
particles are the same.

[0129] Alternatively, by subjecting an inorganic substance (starting
material) and a plurality of mutually different organic compounds to a
hydrothermal synthesis, it is also possible to obtain organic-inorganic
composite particles containing inorganic particles formed of an inorganic
substance that is different from the starting inorganic substance (second
hydrothermal synthesis).

[0130] Examples of the inorganic substance subjected to the second
hydrothermal synthesis include hydroxides, metal complexes, nitrates,
sulfates, and the like. Hydroxides and metal complexes are preferable.

[0131] Examples of the elements contained in the hydroxides (elements that
serve as cations and combine with the hydroxyl ion (Off)) include the
same elements that combine with oxygen in the above-described oxides.

[0133] The metallic elements contained in the metal complexes are those
that form composite oxides with the metals contained in the
above-described hydroxides, and examples include titanium, iron, tin,
zirconium, and the like. Titanium is preferable.

[0134] Examples of ligands in the metal complexes include
monohydroxycarboxylic acids such as 2-hydroxyoctanoic acid; and the like.

[0135] Examples of metal complexes include 2-hydroxyoctanoic acid titanate
and the like. The metal complexes can be obtained from the aforementioned
metallic elements and ligands.

[0136] Examples of the plurality of mutually different organic compounds
include a plurality of mutually different organic compounds as used for
the first hydrothermal synthesis.

[0137] In the second hydrothermal synthesis, an inorganic substance and a
plurality of mutually different organic compounds are reacted under
high-temperature, high-pressure conditions in the presence of water.

[0138] As for the proportions of respective ingredients, the proportion of
the plurality of mutually different organic compounds is, for example, 1
to 1500 parts by mass, preferably 5 to 500 parts by mass, and more
preferably 5 to 250 parts by mass, and the proportion of water is, for
example, 50 to 8000 parts by mass, preferably 80 to 6600 parts by mass,
and more preferably 80 to 4500 parts by mass, per 100 parts by mass of
inorganic compound.

[0139] The total proportion of the plurality of mutually different organic
compounds is, for example, 0.9 to 1880 mL, preferably 4.5 to 630 mL, and
more preferably 4.5 to 320 mL, per 100 g of hydroxide. The total molar
proportion of the plurality of mutually different organic compounds is,
for example, 0.01 to 10000 mol and preferably 0.1 to 10 mol per one mol
of hydroxide.

[0140] The proportion of water is, for example, 50 to 8000 mL, preferably
80 to 6600 mL, and more preferably 100 to 4500 mL, per 100 g of
hydroxide.

[0141] The reaction conditions in the second hydrothermal synthesis are
the same as the reaction conditions in the first hydrothermal synthesis
described above.

[0142] In this manner, organic-inorganic composite particles having a
plurality of mutually different organic groups on the surface of
inorganic particles formed of an inorganic substance that is different
from the starting inorganic substance are obtained.

[0143] The formulation used for the second hydrothermal synthesis may
further include, in addition to the aforementioned ingredients, a
carbonic acid source or a hydrogen source.

[0145] Examples of hydrogen sources include hydrogen (hydrogen gas); acids
such as formic acid and lactic acid; hydrocarbons such as methane and
ethane; and the like.

[0146] The proportion of carbonic acid source or hydrogen source is, for
example, 5 to 140 parts by mass and preferably 10 to 70 parts by mass per
100 parts by mass of inorganic substance.

[0147] Alternatively, the proportion of carbonic acid source is, for
example, 5 to 100 mL and preferably 10 to 50 mL per 100 g of inorganic
substance. The molar proportion of carbonic acid source is, for example,
0.4 to 100 mol, preferably 1.01 to 10.0 mol, and more preferably 1.05 to
1.30 mol, per one mol of inorganic substance.

[0148] Alternatively, the proportion of hydrogen source is, for example, 5
to 100 mL and preferably 10 to 50 mL per 100 g of inorganic substance.
The molar proportion of hydrogen source is, for example, 0.4 to 100 mol,
preferably 1.01 to 10.0 mol, and more preferably 1.05 to 2.0 mol per one
mol of inorganic substance.

[0149] In the high-temperature treatment performed in the plurality of
mutually different organic compounds, the inorganic substance and the
plurality of mutually different organic compounds are blended and heated,
for example, under ordinary pressures. While being subjected to the
high-temperature treatment, the plurality of mutually different organic
compounds serve as organic group-introducing compounds as well as a
solvent for dispersing or dissolving the inorganic substance.

[0150] The total proportion of the mutually different organic compounds
is, for example, 10 to 10000 parts by mass and preferably 100 to 1000
parts by mass per 100 parts by mass of inorganic substance. In terms of
volume, the total proportion of the mutually different organic compounds
is, for example, 10 to 10000 mL and preferably 100 to 1000 mL per 100 g
of inorganic substance.

[0151] The heating temperature is, for example, greater than 100°
C., preferably 125° C. or greater, and more preferably 150°
C. or greater, and usually 300° C. or less and preferably
275° C. or less. The heating time is, for example, 1 to 60 minutes
and preferably 3 to 30 minutes.

[0152] The shape of the organic-inorganic composite particles (primary
particles) obtained in this manner is not particularly limited and is,
for example, anisotropic or isotropic, and the average particle diameter
thereof (maximum length when anisotropic) is, for example, 200 μm or
less, preferably 1 nm to 200 μm, more preferably 3 nm to 50 μm, and
particularly preferably 3 nm to 10 μm.

[0153] As described in detail in the examples below, the average particle
diameter of the organic-inorganic composite particles may be determined
by dynamic light scattering (DLS) and/or calculated from a transmission
electron microscopic (TEM) or scanning electron microscopic (SEM) image
analysis.

[0154] When the average particle diameter is lower than the aforementioned
range, the proportion of the volume of the mutually different organic
groups relative to the surface of the organic-inorganic composite
particles is high, and the function of the inorganic particles is
unlikely to be ensured.

[0155] When the average particle diameter exceeds the aforementioned
range, particles may be crushed when being blended with the resin.

[0156] The organic-inorganic composite particles obtained in this manner
are unlikely to agglomerate in a dry state, and even when the particles
appear to be agglomerated in a dry state, agglomeration (formation of
secondary particles) is inhibited in a particle-dispersed resin
composition as well as in a particle-dispersed resin article, and the
particles are dispersed nearly uniformly as primary particles in the
resin.

[0157] In the organic-inorganic composite particles, the proportion of the
surface area of the organic groups relative to the surface area of the
inorganic particles, i.e., the surface coverage by the organic groups in
the organic-inorganic composite particles (=(surface area of organic
group/surface area of inorganic particle)×100) is usually, for
example, 30% or greater and preferably 60% or greater, and usually 200%
or less.

[0158] In the calculation of surface coverage, first, the shape of the
inorganic particles is determined by transmission electron microscopy
(TEM), the average particle diameter is then calculated, and the specific
surface area of the particles is calculated from the shape of the
inorganic particles and the average particle diameter. Alternatively, the
proportion of the organic groups accounting for the organic-inorganic
composite particles may be calculated from the weight change resulting
from heating the organic-inorganic composite particles to 800° C.
using a differential thermal balance (TG-DTA); the amount of the organic
groups per particle is then calculated from the molecular weight of the
organic groups, the particle density, and the average volume; and the
surface coverage is determined from these factors.

[0159] When at least the surface coverage is high and the organic groups
of the organic-inorganic composite particles have a length sufficient to
cancel the electric charge of the inorganic particles, the kind of
solvent (medium) for dispersing the organic-inorganic composite particles
may be selected (specified or managed) according to the kind of organic
group.

[0160] The organic-inorganic composite particles obtained above may be
subjected to wet classification.

[0161] That is, a solvent is added to the organic-inorganic composite
particles, and the mixture is stirred, left to stand still, and then
separated into supernatant and precipitate. The solvent may be the same
as those described above, and halogenated aliphatic hydrocarbons are
preferable.

[0162] Subsequently, the supernatant is recovered and it is thus possible
to obtain organic-inorganic composite particles having a small particle
diameter.

[0163] Wet classification allows the average maximum length of the
resulting organic-inorganic composite particles (primary particles) to be
controlled so as to be, for example, 3 nm to 450 nm, preferably 3 nm to
200 nm, and more preferably 3 nm to 100 nm.

[0164] The solvent for dispersing the particles obtained above is not
particularly limited and examples include those usable in the
above-described washing. In addition to those solvents, other examples
include alicyclic hydrocarbons such as cyclopentane and cyclohexane;
esters such as ethyl acetate; polyols such as ethylene glycol and
glycerol; nitrogen-containing compounds such as N-methylpyrrolidone,
pyridine, acetonitrile, and dimethylformamide; acryl-based monomers such
as isostearyl acrylate, lauryl acrylate, isoboronyl acrylate, butyl
acrylate, methacrylate, acrylic acid, tetrahydrofurfuryl acrylate,
1,6-hexanediol diacrylate, 2-hydroxyethyl acrylate, 4-hydroxybutyl
acrylate, phenoxyethyl acrylate, and acryloylmorpholine; vinyl
group-containing monomers such as styrene and ethylene; epoxy-containing
compounds such as bisphenol A epoxy; and the like. Aliphatic
hydrocarbons, halogenated aliphatic hydrocarbons, aromatic hydrocarbons,
and ethers are preferable.

[0165] These solvents may be used singly or as a combination of two or
more.

[0166] The proportion of solvent blended is not particularly limited, and
the concentration of organic-inorganic composite particle in the particle
dispersion is adjusted so as to be, for example, 0.1 to 99 mass %,
preferably 1 to 90 mass %, and more preferably 1 to 80 mass %.

[0167] The manner of dispersing particles in a solvent is not particularly
limited, and particles and a solvent may be blended and stirred. The
organic-inorganic composite particles can be dispersed according to such
a simple method. Also, ultrasonication, and other known dispersion
treatments such as bead milling may be performed.

[0168] Accordingly, in the particle dispersion, the organic-inorganic
composite particles are uniformly dispersed as primary particles in a
solvent, i.e., without particle agglomeration.

[0169] Furthermore, even if dried once, the organic-inorganic composite
particles of the present invention can be re-dispersed easily as primary
particles when a solvent is added to the organic-inorganic composite
particles.

[0170] The resin for dispersing the organic-inorganic composite particles
is not particularly limited and examples include thermosetting resins and
thermoplastic resins.

[0173] These resins may be used singly or as a combination of two or more.

[0174] The melting temperature of the resins (in particular, thermoplastic
resins) is, for example, 200 to 300° C., and the softening
temperature is, for example, 150 to 280° C.

[0175] For example, to disperse organic-inorganic composite particles in a
resin, at least organic-inorganic composite particles and a resin are
blended and stirred.

[0176] Preferably, organic-inorganic composite particles, a solvent, and a
resin are blended and stirred to give a particle-dispersed resin fluid,
and the solvent in the particle-dispersed resin fluid is then removed.
Blending a solvent allows the organic-inorganic composite particles to be
more uniformly dispersed in the resin.

[0177] Specifically, a resin solution dissolved in a solvent and the
aforementioned particle dispersion are blended.

[0178] Solvents for use in the preparation of a resin solution may be the
same as those mentioned above and the proportion of solvent is, for
example, 1 to 9900 parts by mass, preferably 40 to 2000 parts by mass,
and more preferably 50 to 1000 parts by mass, per 100 parts by mass of
the resin of the resin solution.

[0179] The resin solution and the particle dispersion is blended such that
the proportion of organic-inorganic composite particle is, for example,
0.1 to 9900 parts by mass, preferably 1 to 9000 parts by mass, and more
preferably 5 to 400 parts by mass, per 100 parts by mass of resin (solids
content). In other words, the concentration of organic-inorganic
composite particle in the particle-dispersed resin composition is, for
example, 0.1 to 99 mass %, preferably 1 to 90 mass %, and more preferably
1 to 80 mass %.

[0180] Meanwhile, to prepare the particle-dispersed resin composition, for
example, if the resin is liquefied at ordinary temperatures (or if it is
in a liquid state) or if the resin melts when heated, it is also possible
that the resin is blended with the organic-inorganic composite particles
without a solvent

[0181] The particle-dispersed resin composition prepared in this manner is
a molten material of the particle-dispersed resin composition that does
not contain a solvent

[0182] When the resin is composed of a thermoplastic resin, the heating
temperature may be the same as the melting temperature of the resin or
greater, and specifically the heating temperature is 200 to 350°
C. When the resin is composed of a thermosetting resin, the heating
temperature may be a temperature at which the state of the resin is at
the B stage, for example, 85 to 140° C.

[0183] The resin and the organic-inorganic composite particles may be
blended such that the concentration of organic-inorganic composite
particle is, for example, 0.1 to 80 mass % and preferably 1 to 70 mass %.

[0184] The particle-dispersed resin composition as obtained above is then
dried by, for example, being heated at 40 to 60° C. to remove the
solvent and to give a particle-dispersed resin composition.

[0185] The obtained particle-dispersed resin composition is then applied
to, for example, a known support so as to prepare a coating, and this
coating is dried to be formed into a particle-dispersed resin article
that is in a film form.

[0186] The particle-dispersed resin composition is applied using, for
example, a known application method such as a spin coater method or a bar
coater method. Simultaneously with or immediately after the application
of the particle-dispersed resin composition, the solvent is removed by
volatilization. If necessary, the solvent may be dried by being heated
after the application of the resin composition.

[0187] The viscosity of the particle-dispersed resin composition during
application may be suitably adjusted by, for example, concentrating the
resin composition with an evaporator or by drying, or through a similar
operation.

[0188] The thickness of the film to be obtained is suitably arranged
according to the use and the purpose, and the thickness is, for example,
0.1 to 2000 μm, preferably 1 to 1000 μm, and more preferably 5 to
500 μm.

[0189] The particle-dispersed resin article can be formed into a film
according to a melt process in which the particle-dispersed resin
composition is extruded with an extruder.

[0190] Also, the particle-dispersed resin composition may be poured into a
metal mold or the like and formed into a block (bulk) by, for example,
thermoforming with a heat press.

[0191] Accordingly, in the particle-dispersed resin article, the
organic-inorganic composite particles are uniformly dispersed as primary
particles in the resin. That is, the organic-inorganic composite
particles do not agglomerate with each other.

[0192] The organic-inorganic composite particles of the present invention
obtained according to the method described above can be dispersed as
primary particles in a solvent and/or a resin in a high proportion,
exhibiting excellent dispersibility in a solvent and/or a resin.

[0193] Therefore, in the particle dispersion and the particle-dispersed
resin composition of the present invention, organic-inorganic composite
particles are dispersed highly uniformly. Moreover, the organic-inorganic
composite particles can be highly uniformly dispersed therein in a high
proportion.

[0194] In particular, the plurality of organic groups are different from
each other, and thus the intermolecular force between the organic groups
and the molecules of the solvent and/or the molecules of the resin is
high and compatibility between the organic groups and the molecules of
the solvent and/or the molecules of the resin is therefore high.

[0195] In detail, when the plurality of organic groups are hydrocarbon
groups each having a different number of carbon atoms, the organic groups
have different sizes (length and/or scale). Therefore, a space (pocket)
is created between the adjacent long-chain and/or bulky homologous
organic groups due to the short-chain and/or less bulky organic groups.
The molecule of a solvent and/or the molecule of a resin enter into the
space, and it is thus possible to enhance interaction between the
long-chain and/or bulky homologous organic groups and the molecule of the
solvent and/or the molecule of the resin. As a result, the dispersibility
of the organic-inorganic composite particles can be enhanced.

[0196] When one organic group is a functional group-containing
hydrocarbon-based organic group and the other organic group is a
hydrocarbon group, since the functional group can be adjusted, it is thus
possible to enhance the compatibility of the entire organic groups with
the solvent and/or the resin.

[0197] Moreover, when the two or more organic groups are functional
group-containing hydrocarbon-based organic groups each having a different
functional group, since the kind and the amount of functional group can
be adjusted, and it is thus possible to enhance the compatibility of the
entire two or more organic groups with the solvent and/or the resin.

[0198] By adjusting the kind and the amount of functional group, the
active site of the organic-inorganic composite particles can also be
controlled.

[0199] It is thus possible to further enhance the dispersibility of the
organic-inorganic composite particles in the solvent and/or the resin.

[0200] Therefore, in the particle dispersion and/or the particle-dispersed
resin composition of the present invention, the organic-inorganic
composite particles are dispersed highly uniformly.

[0201] As a result, when the average particle diameter of the
organic-inorganic composite particles is less than 400 nm or when the
difference in refractive index between the resin and the
organic-inorganic composite particles is small, a particle-dispersed
resin article formed from the particle-dispersed resin composition can
maintain excellent transparency.

[0202] Therefore, a particle-dispersed resin article produced as described
above has excellent optical properties and is usable in various
industrial applications such as optical applications and electromagnetic
wave applications.

[0204] The present invention shall be described in more detail below by
way of examples, comparative examples, preparation examples, and
comparative preparation examples. However, the present invention is not
limited to these examples.

[0205] Organic-inorganic composite particles, particle dispersions, and
films (particle-dispersed resin articles) were evaluated according to the
following methods.

[0206] (1) X-Ray Diffractometry (XRD)

[0207] Glass holders were filled with organic-inorganic composite
particles and X-ray diffractometry was performed thereon under the
following conditions. Thereafter, in reference to the obtained peaks, the
components of the inorganic compounds were assigned through database
search.

[0219] (3) Determination of Average Particle Diameter and Evaluation of
Dispersibility

[0220] (a) Average Particle Diameter

[0221] Organic-inorganic composite particles were dispersed in a solvent
(a good solvent in which the organic-inorganic composite particles were
dispersed as primary particles, such as cyclohexane, chloroform, hexane,
toluene, ethanol, or aqueous ammonia) to prepare a sample (a solids
concentration of 1 mass % or less), and the average particle diameter of
the organic-inorganic composite particles in the sample was measured with
a dynamic light scattering photometer (model number: "ZEN3600", DLS,
manufactured by a Sysmex Corporation).

[0222] (b) Dispersibility

[0223] The dispersibility of a particle dispersion was measured with a
dynamic light scattering photometer (model number: "ZEN3600",
manufactured by a Sysmex Corporation). The average particle diameter thus
measured was compared with the average particle diameter measured using 1
μM or SEM. If the measured diameters were identical, the dispersion
was evaluated as having good dispersibility, and if the measured
diameters were greatly different, the dispersion was evaluated as having
poor dispersibility.

[0224] (4) Agglomerating Properties

[0225] The particle dispersion and the film was visually observed by SEM
and TEM for the presence or absence of an agglomerate.

[0226] (5) Observation with Transmission Electron Microscope (TEM)

[0227] (a) Determination of Average Particle Diameter

[0228] A particle dispersion (a solids concentration of 1 mass % or less)
of organic-inorganic composite particles diluted with a solvent was
dropped onto a TEM grid (collodion film, carbon supporting film) and
dried, and organic-inorganic composite particles were visually observed
with a transmission electron microscope (TEM). An image analysis was
performed to calculate the average particle diameter of the
organic-inorganic composite particles.

[0229] (b) Evaluation of Dispersibility and Agglomerating Properties of
Organic-Inorganic Composite Particles in Film

[0230] Film was cut, and the cut surface was visually observed with a
transmission electron microscope (TEM, H-7650, manufactured by Hitachi
High-Technologies Corp.) to examine the state of dispersion of
organic-inorganic composite particles.

[0231] In the TEM observation, film was embedded in an epoxy resin and cut
so as to form a clear cut surface of the film.

[0232] (6) Observation with Scanning Electron Microscope (SEM)

[0233] (a) Determination of Particle Having Average Particle Diameter of
No Less than 200 nm.

[0234] A particle dispersion was dripped onto a sample stage, dried, and
visually observed with a scanning electron microscope (SEM, S-4800,
manufactured by Hitachi High-Technologies Corp., or JSM-7001F,
manufactured by JEOL Ltd.) to see the shape and the average particle
diameter of organic-inorganic composite particles.

[0235] (b) Evaluation of Dispersibility and Agglomerating Properties in
Film of Particle Having Average Particle Diameter of No Less than 200 nm

[0236] Film was cut, and the cut surface was visually observed with a
scanning electron microscope (SEM, S-4800, manufactured by Hitachi
High-Technologies Corp.) to see the dispersed state of organic-inorganic
composite particles. The film was embedded in an epoxy resin and cut so
as to form a clear cut surface of the film.

Preparation of Organic-Inorganic Composite Particles

Example 1

[0237] Cerium hydroxide (Ce(OH)4, manufactured by Wako Pure Chemical
Industries, Ltd.) serving as an inorganic compound, decanoic acid and
hexanoic acid serving as two kinds of organic compounds, and water were
charged into a 5 mL high-pressure reactor (SHR-R6-500, manufactured by
AKICO Corporation) in amounts presented in Table 1.

[0238] The lid of the high-pressure reactor was closed, the reactor was
heated to 400° C. in a shaking heating furnace (manufactured by
AKICO Corporation), the pressure inside the high-pressure reactor was
increased to about 40 MPa due to the amount of water present therein, and
shaking was performed for 10 minutes to carry out a hydrothermal
synthesis.

[0239] Thereafter, the high-pressure reactor was rapidly cooled by being
placed in cold water.

[0240] Ethanol was then added and stirred, and centrifugation was
performed at 15000 G for 20 minutes in a centrifuge (trade name: MX-301,
Tomy Seiko Co., Ltd.) to isolate the precipitate (reaction product) from
the supernatant (washing step). This washing step was repeated 5 times.
Ethanol in the precipitate was then dried by heating at 80° C.,
giving organic-inorganic composite particles containing a decyl group and
a hexyl group, i.e., the two kinds of organic groups, on the surface of
cerium oxide (CeO2).

[0241] The organic-inorganic composite particles obtained above and
chloroform were charged into a screw cap vial and centrifuged at 4000 G
for 5 minutes with a centrifuge (trade name: MX-301, manufactured by Tomy
Seiko Co. Ltd.) to separate into a supernatant and a precipitate (wet
classification).

[0242] The supernatant was then isolated and dried to give
organic-inorganic composite particles having a small particle diameter.

[0244] As a result, (1) XRD confirmed that the inorganic compound forming
the inorganic particles was CeO2.

[0245] (2) FT-IR confirmed that different saturated aliphatic groups
(decyl group and hexyl group) were present on the surface of the
inorganic particles.

[0246] (3) DLS showed that the average particle diameter of the
organic-inorganic composite particles was 7 nm. (5) TEM showed that the
average particle diameter of the organic-inorganic composite particles
was 4 to 10 nm.

[0247] The results described above are presented in Table 1.

Examples 2 to 131 and Comparative Examples 1 to 12

[0248] Organic-inorganic composite particles were prepared in the same
manner as in Example 1 except that the inorganic substance (inorganic
particles), the organic compounds, and water were used according to the
formulations presented in Tables 1 to 8. In wet classification,
centrifugal gravitational acceleration was suitably altered and, if
necessary, filtration with a 100-nm filter was performed.

[0249] Then, the obtained organic-inorganic composite particles were
evaluated in the same manner as in Example 1. Results are presented in
Tables 1 to 8.

[0250] According to Tables 9 to 19, the organic-inorganic composite
particles of each example and a good solvent (a solvent that has
compatibility with the mutually different organic groups) were blended so
as to prepare particle dispersions having an organic-inorganic composite
particle concentration of 1 mass %.

[0253] Dispersibility was evaluated according to the following criteria:

[0254] Good: In a particle dispersion where organic-inorganic composite
particles were dispersed in a solvent, the precipitate after 1 day
accounted for less than 1 wt %, and the organic-inorganic composite
particles were dispersed as primary particles nearly uniformly in the
solvent.

[0255] Fair: In a particle dispersion where organic-inorganic composite
particles were dispersed in a solvent, the precipitate after 1 day
accounted for less than 1 wt %, and the organic-inorganic composite
particles were dispersed nearly uniformly in the solvent; or the
precipitate after 1 day accounted for 1 wt % to less than 10 wt %, and
the organic-inorganic composite particles were dispersed as primary
particles nearly uniformly in the solvent.

[0256] Poor: In a particle dispersion where organic-inorganic composite
particles were dispersed in a solvent, the precipitate after 1 day
accounted for 10 wt % or greater, and the organic-inorganic composite
particles were agglomerated in the solvent.

TABLE-US-00015
TABLE 15
Organic-inorganic composite particle Dispersibility evaluation
Composition Mass % of organic-inorganic composite particle in
of inorganic particle dispersion (solvent: chloroform)
No. particle Surface organic group 1 10 30 40 50 60 70 80
Ex. 1 CeO2 Decyl group Hexyl group Good Good Good Good Good Good Fair
Fair
Ex. 28 CeO2 2-Ethylhexyl group Hexyl group Good Good Good Good Good
Good Good Fair
Ex. 5 CeO2 6-Phenylhexyl group Phenyl group Good Good Good Good Good
Good Good Fair

[0257] A polyarylate resin (polyarylate resin of Example 4 of Japanese
Unexamined Patent Publication No. 2009-80440) was blended with good
solvents of Tables 20 to 22 (cyclohexane, chloroform, hexane, toluene,
ethanol, and aqueous ammonia) so as to prepare resin solutions having a
solids concentration of 10 mass %.

[0258] The particles of Examples 1, 3 to 10, 12, 13, 19, 20, 27, 28, 43 to
46, 49 to 55, 59, 66, 67, 117 and 120 to 124 were blended with the good
solvents of Tables 20 to 22 so as to prepare particle dispersions having
a solids concentration of 10 mass %.

[0259] The resin solutions and the particle dispersions were then blended
such that the proportion of organic-inorganic composite particle was 10
mass % relative to the total amount of resin and organic-inorganic
composite particle, and the organic-inorganic composite particles were
dispersed in the resin solutions using an ultrasonic disperser, thus
giving transparent particle-dispersed resin composition varnishes.

[0260] Next, the obtained varnishes were applied to a support using a spin
coat method.

[0261] The applied particle-dispersed resin compositions were then dried
at 50° C. for 1 hour (first-stage drying) and dried at 100°
C. for 10 minutes (second-stage drying) so as to prepare films having a
thickness of 8 μm (particle-dispersed resin articles).

[0262] Thereafter, the obtained films were evaluated in terms of (4)
agglomerating properties described above.

[0263] The criteria of agglomerating property evaluation are given below:

[0266] While the illustrative embodiments of the present invention were
provided in the above description, they are for illustrative purposes
only and not to be construed limiting. Modification and variation of the
present invention that will be obvious to those skilled in the art is to
be covered by the following claims.